A solid laser, semiconductor laser and gas laser having a large output and a small size, which radiate an ultraviolet ray, visible light or infrared ray having a wavelength of from 300 to 1,200 nm, have become easily available, and these lasers are very advantageous for a recording light source used in the direct plate-making based on digital signal, for example, from a computer.
Various investigations on recording materials sensitive to such laser beams have been made. Representative examples of the recording material include first positive working recording materials capable of being recorded with an infrared laser having a wavelength of not shorter than 760 nm (as described, for example, in Patent Document 1) and negative working recording materials of acid catalyst crosslinking type (as described, for example, in Patent Document 2), and second recording materials responsive to an ultraviolet ray or visible light laser having a wavelength of from 300 to 700 nm, for example, negative working recording materials of radical polymerization type (as described, for example, in Patent Documents 3 and 4).
On the other hand, polymerizable compositions curable with light having a short wavelength of not longer than 300 nm or an electron beam are especially important for photoresist materials. In recent years, the degree of integration is more and more increased in integrated circuits, and the fabrication of ultra-fine patterns composed of lines having a width of finer than a half micron has been required in the production of semiconductor substrate, for example, VLSI. In order to fulfill such requirements, the wavelength of light source for an exposure apparatus used in photolithography is more and more shortened and the use of a far ultraviolet ray or an excimer laser beam (e.g., XeCl, KrF or ArF) has been investigated. Further, the formation of ultra-fine patterns by an electron beam has been started to investigate. Particularly, the electron beam is regarded as a promising light source for the next generation pattern formation techniques.
A problem common to all of these image-forming materials is that how a balance between film strength and preservation stability of a photosensitive layer can be achieved. In particular, it is required for a recording material as a lithographic printing plate precursor to have large film strength in view of printing durability. However, it is a difficult problem to be resolved that both the film strength and the preservation stability of a photosensitive layer are improved at the same time, and a sufficiently satisfactory result cannot be obtained by conventional techniques. Thus, a novel technique different from conventional techniques has been requested.
In order to resolve the problem, a technique of introducing a polymerizable group into an alkali-soluble resin (as described, for example, in Paten Document 5) has beep proposed. In the technique, however, a difference between reactivity of the polymerizable group introduced into the alkali-soluble resin and reactivity of a polymerizable group of the polymerizable compound is small. Therefore, an effect of increase in reaction rate of the polymerizable group is not sufficiently obtained under present circumstances because of less mobility and poor reactivity of polymerizable group radical present in the resin, although reactions between the polymerizable groups introduced into the resin frequently occur.
Patent Document 1: U.S. Pat. No. 4,708,925
Patent Document 2: JP-A-8-276558 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)
Patent Document 3: U.S. Pat. No. 2,850,445
Patent Document 4: JP-B-44-20189 (the term “JP-B” as used herein means an “examined Japanese patent publication”)
Patent Document 5: JP-A-2000-187322